alias_attribute does not work when building has_many records via relation.

[dewyze]

Steps to reproduce

require "bundler/inline"

gemfile(true) do
  source "https://rubygems.org"
  gem "activerecord", "7.1.3.2"
  gem "sqlite3"
end

require "active_record"
require "minitest/autorun"
require "logger"

# This connection will do for database-independent bug reports.
ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:")
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Schema.define do
  create_table :users, force: :cascade do |t|
  end

  create_table :posts, force: :cascade do |t|
    t.integer :person_id
  end
end

class User < ActiveRecord::Base
  has_many :posts,
    inverse_of: :user
end

class Post < ActiveRecord::Base
  alias_attribute :user_id, :person_id

  belongs_to :user
end

class BugTest < Minitest::Test
  def test_association
    user = User.create!

    assert Post.create(user: user)        # Success
    assert Post.create(user_id: user.id)  # Success
    assert user.posts.create!             # Failure
  end
end

Expected behavior

Post.create(user: user) works fine. But when creating the associated record via user.posts.create! it breaks because the foreign key is not getting set properly.

ActiveModel::MissingAttributeError: can't write unknown attribute `user_id`
          raise ActiveModel::MissingAttributeError, "can't write unknown attribute `#{name}`"

Additionally, we cannot specify belongs_to :user, foreign_key: :user_id or has_many :posts, inverse_of: :user, foreign_key: :user_id. One of those has to at least set foreign_key: :person_id for this to work.

Actual behavior

The has_many association calls set_owner_attributes:

rails/activerecord/lib/active_record/associations/has_many_association.rb

Line 62 in 6f0d1ad

set_owner_attributes(record)

Set owner attributes is called and gets the foreign key:

rails/activerecord/lib/active_record/associations/foreign_association.rb

Line 25 in 6f0d1ad

primary_key_attribute_names = Array(reflection.join_primary_key)

If it's not specified, the name is derived, in this case user_id when the has many checks the inverse belongs_to:

rails/activerecord/lib/active_record/reflection.rb

Lines 773 to 783 in 6f0d1ad

	def derive_foreign_key(infer_from_inverse_of: true)
	if belongs_to?
	"#{name}_id"
	elsif options[:as]
	"#{options[:as]}_id"
	elsif options[:inverse_of] && infer_from_inverse_of
	inverse_of.foreign_key(infer_from_inverse_of: false)
	else
	active_record.model_name.to_s.foreign_key
	end
	end

Then we call _write_attribute:

rails/activerecord/lib/active_record/associations/foreign_association.rb

Line 32 in 6f0d1ad

record._write_attribute(primary_key, value)

This raises the error since _write_attribute does not reference aliases.

write_attribute would work:

rails/activerecord/lib/active_record/attribute_methods/write.rb

Line 33 in 6f0d1ad

name = self.class.attribute_aliases[name] || name

But @byroot mentions here a possible high cost to doing that.

I'm happy to help implement a solution, but not sure exactly where it should live. I don't know if doing it in the foreign key lookup would be cheaper at all, but it still requires a call to <record_class>.attribute_aliases.

System configuration

Rails version: 7.1.3.2

Ruby version: 3.1.0

[byroot]

Not sure if we really want to change this.

In your case I believe you can easily fix this with:

has_many :posts, inverse_of: :user, foreign_key: :person_id

[dewyze]

Yeah, we can make that work. But in the case of trying to rename a class, column, etc. The presence of those can still be confusing.

If we don't want to introduce this that's fine, but I wanted to check first if this was the intended behavior.